Nowadays, a communications architecture in the communications industry is basically established according to seven layers of communications protocols of an Open System Interconnection (OSI) model. The seven-layer of communications protocols are: a physical layer, a link layer, a network layer, a transport layer, a session layer, a presentation layer, and an application layer.
The CPRI protocol is a data transmission protocol applied at the link layer. Further, the CPRI protocol is formulated by communications equipment manufacturers and is a standard of an interface between a radio equipment controller (REC) and radio equipment (RE) that are in a radio base station. The CPRI protocol mainly includes three aspects: the 8b10b encoding and decoding protocol that is used to discover a link transmission error, and a scrambling and descrambling solution that is used to ensure a good signal randomness; the High-level Data Link Control (HDLC) protocol and the Ethernet (ETH) protocol that are used to establish a connection network at the network layer; and a control word format solution for control information required for link synchronization and link maintenance.
In order to ensure correct transmission of a signal between an REC and an RE, it is necessary to ensure that the foregoing three aspects of the REC and the RE are in a good operation state. A CPRI negotiation state machine can reflect whether the foregoing three aspects are in a good operation state. Further, the CPRI negotiation state machine is disposed on both the REC and the RE. Before data transmission is performed between the REC and the RE, the CPRI negotiation state machine of the REC may negotiate with the CPRI negotiation state machine of the RE, and the data transmission between the REC and the RE starts only after it is confirmed that the foregoing three aspects are in a normal state.
In the existing CPRI protocol, a negotiation process between the CPRI negotiation state machine of the REC and the CPRI negotiation state machine of the RE mainly includes L1 layer (physical layer) synchronization negotiation, CPRI protocol version number negotiation, and HDLC capability and ETH capability negotiation. After the CPRI negotiation state machine of the REC and the CPRI negotiation state machine of the RE reach an agreement on the foregoing three aspects through negotiation, they transit to a same normal working state. In this case, the data transmission between the REC and the RE starts. During the data transmission between the REC and the RE, periodic negotiation is performed between the CPRI negotiation state machine of the REC and the CPRI negotiation state machine of the RE. Once states of the two state machines are inconsistent, the data transmission between the REC and the RE stops. It can be seen that, the CPRI negotiation state machines can ensure correct transmission of a signal between the REC and the RE.
At present, a CPRI negotiation state machine is implemented mainly by a hardware product, such as a chip. It is difficult to determine an evolution or change trend of the CPRI protocol, so CPRI protocols that can be supported by manufactured hardware products are very limited. After the CPRI protocol evolves or changes, an existing hardware product cannot be compatible with the latest CPRI protocol. The evolution of the existing CPRI protocol speeds up, which results in that the service life of the existing hardware product is greatly shortened and production costs of manufacturers are increased.